I have just run a "free"programme called spyware4 which claims to have found 1768 threats to my computer, when I click on 'Fix threats' it requires €35.69 from me to do so. Should I pay this, or try something else please?
never run programmes offered to you over the internet. Do as others have suggested: download the free Malwarebytes and run it once a week. Plus have something like MSE or Avast (also free) running all the time.
You will probably find that the only threat on your computer was this spyware4. Unfortunately, it's due to people paying money to these con merchants that persuades them to keep these things going.